Several somatic cell hybrids formed by fusion of mouse-erythroleukemia cells and human fibroblasts and known to contain human chromosome 11 by virtue of the presence of human LDH-A, were analyzed for their globin gene and mRNA content. The human gamma and beta genes were identified but only beta and not gamma mRNA was found in the cytoplasm. A low level of human beta globin production was identified in these hybrid cells by a sensitive radioimmunoassay.